Canon SPEEDLITE EL-1 Advanced User's Manual page 37

About the Auto Power OFF Function
To save battery power, the power will turn off automatically after approx. 90 sec. of idle use.
To turn on the Speedlite again, press the camera's shutter button halfway or press the test
flash button (flash-ready lamp).
When set as the sender unit for radio transmission wireless flash shooting ( ) or set for
linked shooting ( ), the time until auto power off takes effect is approx. 5 min.
Note
Auto power off can be disabled (C.Fn-01).
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